The present invention relates to a process for machining axial blade slots in turbine disks for jet engines.
Retention slots are a design feature of turbine disks. The slots are used to hold or retain turbine blades around the periphery of the disk. Current practice in the aerospace industry is to machine these slots into the disk by use of a broaching machine, which is a linear cutting machine that drives successively larger cutters through the disk slot, with the final cutters having the fir tree or other appropriate shape of the finished slot. One technique which employs broaching is illustrated in U.S. Pat. No. 5,430,936 to Yadzik, Jr. et al. Broaching presents a number of issues, including costly cutter tools, very long tooling lead-time, very long tooling set-ups, and a very large single-purpose machine requiring a special concrete base and other infrastructure to support it.
Another method for producing profiled parts is illustrated in U.S. Pat. No. 5,330,326 to Kuehne et al. The method involves pre-shaping and finish grinding a blank in one chucking position with at least one profiled grinding wheel. The blank is translated and rotated relative to the at least one profiled grinding wheel during the pre-shaping step for giving the blank approximately a desired profile. The finished grinding step is performed at least partially after the pre-shaping step for smoothing surfaces and producing the final profile. The Kuehne et al. method may be used for external surfaces, such as the cutting of blades, and not internal surfaces. Thus, Kuehne et al.'s method is not applicable to the creation of internal slots.
There remains a need for a better approach to form the axial blade slots in a turbine disk.